/**
 * Copyright (C) 2002-2015   The FreeCol Team
 * <p>
 * This file is part of FreeCol.
 * <p>
 * FreeCol is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 2 of the License, or
 * (at your option) any later version.
 * <p>
 * FreeCol is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * <p>
 * You should have received a copy of the GNU General Public License
 * along with FreeCol.  If not, see <http://www.gnu.org/licenses/>.
 */

package net.sf.freecol.common.networking;

import net.sf.freecol.common.model.Game;
import net.sf.freecol.common.model.Goods;
import net.sf.freecol.common.model.Player;
import net.sf.freecol.common.model.Settlement;
import net.sf.freecol.common.model.Unit;
import net.sf.freecol.server.FreeColServer;
import net.sf.freecol.server.model.ServerIndianSettlement;
import net.sf.freecol.server.model.ServerPlayer;

import org.w3c.dom.Element;


/**
 * The message sent when purchasing at an IndianSettlement.
 */
public class BuyMessage extends DOMMessage
{

    /** The object identifier of the unit that is buying. */
    private final String unitId;

    /** The object identifier of the settlement that is selling. */
    private final String settlementId;

    /** The goods to be bought. */
    private final Goods goods;

    /** The price to pay. */
    private final String goldString;


    /**
     * Create a new <code>BuyMessage</code>.
     *
     * @param unit The <code>Unit</code> that is buying.
     * @param settlement The <code>Settlement</code> that is trading.
     * @param goods The <code>Goods</code> to buy.
     * @param gold The price of the goods.
     */
    public BuyMessage( Unit unit, Settlement settlement, Goods goods,
                       int gold )
    {
        super( getXMLElementTagName( ) );

        this.unitId = unit.getId( );
        this.settlementId = settlement.getId( );
        this.goods = goods;
        this.goldString = Integer.toString( gold );
    }

    /**
     * Create a new <code>BuyMessage</code> from a
     * supplied element.
     *
     * @param game The <code>Game</code> this message belongs to.
     * @param element The <code>Element</code> to use to create the message.
     */
    public BuyMessage( Game game, Element element )
    {
        super( getXMLElementTagName( ) );

        this.unitId = element.getAttribute( "unit" );
        this.settlementId = element.getAttribute( "settlement" );
        this.goods = new Goods( game,
                                DOMMessage.getChildElement( element, Goods.getXMLElementTagName( ) ) );
        this.goldString = element.getAttribute( "gold" );
    }


    // Public interface

    /**
     * What is the price currently negotiated for this transaction?
     *
     * @return The current price.
     */
    public int getGold( )
    {
        try
        {
            return Integer.parseInt( goldString );
        }
        catch ( NumberFormatException e )
        {
            return - 1;
        }
    }


    /**
     * Handle a "buy"-message.
     *
     * @param server The <code>FreeColServer</code> handling the message.
     * @param player The <code>Player</code> the message applies to.
     * @param connection The <code>Connection</code> message was received on.
     * @return An update following the purchase, or an error
     *     <code>Element</code> on failure.
     */
    public Element handle( FreeColServer server, Player player,
                           Connection connection )
    {
        final ServerPlayer serverPlayer = server.getPlayer( connection );

        Unit unit;
        try
        {
            unit = player.getOurFreeColGameObject( unitId, Unit.class );
        }
        catch ( Exception e )
        {
            return DOMMessage.clientError( e.getMessage( ) );
        }

        ServerIndianSettlement settlement;
        try
        {
            settlement = ( ServerIndianSettlement ) unit.getAdjacentIndianSettlementSafely( settlementId );
        }
        catch ( Exception e )
        {
            return DOMMessage.clientError( e.getMessage( ) );
        }

        // Make sure we are trying to buy something that is there
        if ( goods.getLocation( ) != settlement )
        {
            return DOMMessage.clientError( "Goods " + goods.getId( )
                                                   + " is not at settlement " + settlementId );
        }

        int gold = getGold( );
        if ( gold < 0 ) return DOMMessage.clientError( "Bad gold: " + goldString );

        // Try to buy.
        return server.getInGameController( )
                .buyFromSettlement( serverPlayer, unit, settlement, goods, gold );
    }

    /**
     * Convert this BuyMessage to XML.
     *
     * @return The XML representation of this message.
     */
    @Override
    public Element toXMLElement( )
    {
        Element result = createMessage( getXMLElementTagName( ),
                                        "unit", unitId,
                                        "settlement", settlementId,
                                        "gold", goldString );
        result.appendChild( goods.toXMLElement( result.getOwnerDocument( ) ) );
        return result;
    }

    /**
     * The tag name of the root element representing this object.
     *
     * @return "buy".
     */
    public static String getXMLElementTagName( )
    {
        return "buy";
    }
}
